Now open your browser and go to your HDA and click on the webmin app you already installed, click continue to this website at the cert warning.

Enter user and password as required.

It should look like this:

First test that you've set the job up correctly within Webmin. You can do this by clicking on the job you've just created from the long list of cron jobs (not checking the box but clicking on the name). In the new window that opens click the Run Now button at the bottom of the screen. You should see a message similar to the one you saw when you tested it from a Putty/Terminal session.